1. Technical Field
The present invention relates to an image forming apparatus including an electrophotographic device, such as an electrostatic copier, a printer, a facsimile, or the like, which includes an image carrier, on which at least an electrostatic latent image is formed, and a charge roller for non-contact charging the image carrier by bringing gap members fixed on both ends thereof into contact with the image carrier and setting a predetermined charge gap with respect to the image carrier, and applies at least an alternating current (AC) charge bias to the charge roller.
2. Related Art
In the related art, as an image forming apparatus, an image forming apparatus which forms a predetermined charge gap and has a charge roller for non-contact charging an image carrier to perform a non-contact charging method is disclosed in JP-A-2001-296723. In the charge roller used in the image forming apparatus disclosed in JP-A-2001-296723, a resistance layer formed of a conductive elastic member is provided on the outer circumferential surface of a core, a pair of gap members of formed of an insulating film member having a stripe shape are wound in a ring shape to be adhered, and the pair of gap members are brought into contact with the outer circumferential surface of a photosensitive drum which is the image carrier such that the predetermined charge gap is set between the photosensitive drum and a charge portion of the charge roller between the pair of gap members.
Since the charge portion of the charge roller non-contact charges the photosensitive drum via the charge gap such that ozone can be suppressed from being generated and an extraneous material such as a toner attached to the photosensitive drum can be prevented from being attached to the charge roller or a material included in the resistance layer of the charge roller can be prevented from being attached, the capability of charging the photosensitive drum by the charge roller can be improved.
However, in the above-described non-contact charging method, if the charge gap between the photosensitive layer of the photosensitive body and the charge roller is uneven or a rapid environment variation occurs, charging failure may occur and thus image formation failure may occur. Accordingly, in the related art, this problem was solved by applying a charge bias, which is obtained by superposing a direct current (DC) voltage on an AC voltage, to the charge roller.
However, when the charge bias obtained by superposing the direct current (DC) voltage on the AC voltage is applied to the charge roller, the charge roller may vibrate due to the existence of the AC voltage and thus continuous vibration sound may be generated from the photosensitive body due to the vibration of the charge roller. This is because the charge gap is as small as about 20 μm, air in a minute gap between the photosensitive body and the charge roller exhibits a viscous property with respect to the vibration of the charge roller, and thus the photosensitive body and the charge roller integrally vibrate due to the existence of the viscous property of air.
Accordingly, a technology for suppressing the vibration sound of a photosensitive body by completely or substantially filling an elastic vibration suppression member, such as rubber, in the photosensitive body is suggested in JP-A-2003-302870. In the photosensitive body disclosed in JP-A-2003-302870, since the vibration sound of the photosensitive body is absorbed by the elastic vibration suppression member filled in the photosensitive body, the vibration sound of the photosensitive body is suppressed from being generated although the charge roller vibrates when the AC voltage is applied to the charge roller.